Ingestible capsules are well-known in the prior art. Such capsules are generally small pill-like devices that can be ingested or swallowed by a patient. It is known that such capsules may include one or more sensors for determining physiological data. It is further known that these sensors may be powered by batteries contained within the body of the capsule. The batteries used in such capsules need to be activated shortly before they are used in order to maximize battery lifetime.
A number of methods for controlling the activation and deactivation of the electronics in an ingestible capsule are known in the prior art. However, each of these methods has significant drawbacks regarding its performance. One such method uses an “active” reed switch system. In this system, an external magnetic field actively holds a reed switch so that the circuit remains open. When the ingestible capsule is removed from the magnetic field, the reed switch closes the circuit thereby activating the capsule. One major drawback of this design is its inability to turn off the capsule once it has been activated without having two magnets, internal and external, maintained in alignment.
Another method uses a passive reed switch and magnetizable bias magnet asymmetric design manipulated by an external magnet. The circuitry of the capsule can be selectively switched on and off depending on the magnetic state of the bias magnet which determines the reed switch on/off state. This design, however, suffers from a high failure rate when attempting to deactivate the capsule, also leading to a large number of wasted capsules.
Another method uses materials which dissolve under specific pH conditions, such as the low pH of the stomach. Once the capsule reaches an area of the gastrointestinal tract with the proper pH for dissolving the material, the previously open circuit is able to close, thus activating the capsule electronics. This system, however, has numerous disadvantages, including the inability to determine whether the activation components and capsule are functional before ingestion, the inability to calibrate the capsule sensors prior to ingestion, and the inability to acquire data for portions of the GI tract before the capsule enters a specific pH domain.
Other systems use external triggers which are sent through body tissue to activate the capsule once it has been ingested. Examples of these triggers are RF bursts, magnetic fields, or light. However, these systems suffer the same drawbacks as the pH dissolving activation capsules.
Thus, there is a need for a reliable method for the activation and deactivation of an ingestible capsule.